1. Field of the Invention
The present invention relates to bicycles and, more particularly, to a derailleur system for bicycle.
2. Description of the Related Art
Regular bicycles commonly use a chain transmission mechanism to transmit rotary driving force from the pedal and crank set to the rear wheel. When riding a bicycle, the drive chain may fall out of the chain wheel. There are bicycles with a front or rear derailleur for transmitting driving force from the chain transmission mechanism to the front or rear wheel of the bicycle. The bicycle rider can shift the gear position of the derailleur only when propelling the bicycle. A derailleur of this design is heavy and complicated. When riding, the rider""s pants tend to be contaminated with the lubricating oil of the chain transmission mechanism.
The present invention has been accomplished to provide a derailleur system for bicycle, which eliminates the aforesaid drawbacks. It is the one object of the present invention to provide a derailleur system for bicycle, which eliminates the use of a chain transmission mechanism. It is another object of the present invention to provide a derailleur system for bicycle, which enables the bicycle rider to shift the gear when the bicycle stopped.
To achieve these objects of the present invention, the derailleur system adapted for connecting a speed-changing controller of a bicycle comprises an annular plate having a center axle hole coupled to an axle of the bicycle for synchronous rotation, at least two gears mounted on the annular plate and coaxially arranged around said center axle hole, a bracket assembly rotatably mounted to said center axle hole of said annular plate, a transmission shaft pivoted to said bracket assembly, a driven gear wheel set, a control device and a driven member. The transmission shaft has a longitudinally extended receiving hole. The driven gear wheel set is mounted on said transmission shaft around said receiving hole, said driven gear wheel set including at least two driven gear wheels respectively meshed with the gears, keeping the axis of said driven gear wheel set and the axis of said gear disposed perpendicular to each other on the same plane, each driven gear wheel of said driven gear wheel set having a circular center hole for the passing of said transmission shaft and a retaining portion in said circular center hole at one side. The control device is axially movably inserted into said transmission shaft and connected to a derailleur cable of the bicycle, said control device having a bearing portion. The driven member is mounted and supported on a spring at said bearing portion of said control device for moving with said control device, said driven member having a stop portion protruded from a top sidewall thereof and adapted for engaging the retaining portion of one driven gear wheel of said driven gear wheel set.